2. The sensitization rates to allergic pollen
Allergic sensitization rate for tree pollens has been increased from year to year. The first pollen observations tended to be moved forward and increased the duration of pollen seasons. The sensitization to tree pollens was gradually increased for the last 22 years (Table 2). Sensitization to oak, hazel, and alder pollens had the highest rate of increase (0.28% annually), followed by that to birch, willow, and pine pollens (0.25%, 0.25%, and 0.23%, respectively) (Table 2). Regarding age distribution changes for the last 22 years, sensitization rate to pollens was increased in <10 age of years (Age 3~5 years: 8.3%, 6~9 years: 14.4%, 10~12 years: 24.0%, 13~15 years: 25.4%, and 16~18 years: 27.6 at 1998; Age 3~5 years: 10.7%, 6~9 years: 17.7%, 10~12 years: 22.5%, 13~15 years: 23.9%, and 16~18 years: 25.3 at 2019) (Fig. 1).